Messages in this thread | | | Date | Mon, 06 Oct 2014 12:04:32 +0200 | From | Marek Szyprowski <> | Subject | Re: [PATCH v2] cma: make default CMA area size zero for x86 |
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Hello,
On 2014-10-05 15:54, Akinobu Mita wrote: > This makes CMA memory area size zero for x86 in default configuration > (doesn't change on the other architectures). If default CMA size is > zero, DMA_CMA is disabled. It can be enabled by passing cma= to the > kernel. > > This makes less impact on x86. Because there is no mainline driver that > requires it for x86, and Peter Hurley reported the performance > regression, as this is trying to drive _all_ dma mapping allocations > through a _very_ small window. > > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> > Reported-by: Peter Hurley <peter@hurleysoftware.com> > Cc: Peter Hurley <peter@hurleysoftware.com> > Cc: Chuck Ebbert <cebbert.lkml@gmail.com> > Cc: Jean Delvare <jdelvare@suse.de> > Cc: Marek Szyprowski <m.szyprowski@samsung.com> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Cc: David Woodhouse <dwmw2@infradead.org> > Cc: Don Dutile <ddutile@redhat.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Andi Kleen <andi@firstfloor.org> > Cc: Yinghai Lu <yinghai@kernel.org> > Cc: x86@kernel.org > Cc: iommu@lists.linux-foundation.org
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
> --- > * v2 > - Add information in help text, suggested by Chuck Ebbert > > drivers/base/Kconfig | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig > index 4e7f0ff..115882f 100644 > --- a/drivers/base/Kconfig > +++ b/drivers/base/Kconfig > @@ -240,18 +240,24 @@ comment "Default contiguous memory area size:" > config CMA_SIZE_MBYTES > int "Size in Mega Bytes" > depends on !CMA_SIZE_SEL_PERCENTAGE > + default 0 if X86 > default 16 > help > Defines the size (in MiB) of the default memory area for Contiguous > - Memory Allocator. > + Memory Allocator. If the size of 0 is selected, CMA is disabled by > + default, but it can be enabled by passing cma=size[MG] to the kernel. > + > > config CMA_SIZE_PERCENTAGE > int "Percentage of total memory" > depends on !CMA_SIZE_SEL_MBYTES > + default 0 if X86 > default 10 > help > Defines the size of the default memory area for Contiguous Memory > Allocator as a percentage of the total memory in the system. > + If 0 percent is selected, CMA is disabled by default, but it can be > + enabled by passing cma=size[MG] to the kernel. > > choice > prompt "Selected region size"
Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
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